Searching for inhibitors of fungal 17β-hydroxysteroid dehydrogenase.

17β-Hydroxysteroid dehydrogenases (17β-HSDs) have key roles in hormonal regulation and function in the human, and as such they represent emerging therapeutic targets for the control of estrogen- and androgen-dependent diseases. Our model enzyme is 17β-HSD from the fungus Cochliobolus lunatus (17β-HSDcl), and we have used different approaches to find potent inhibitors of this enzyme. Using “classical” inhibition assays, we have shown that some phytoestrogens and cinnamic acid esters are potent in their inhibition of the oxidation of 4-estrene-17β-ol-3-one and the reduction of 4-estrene-3,17-dione catalyzed by 17β-HSDcl. We have also examined peptides as potential inhibitors of 17β-HSDcl on the basis that this enzyme is a homodimer under native conditions. Thus, compounds that specifically prevent the formation of dimers could represent a new class of inhibitors, since dimerization is a prerequisite for catalysis. We have shown that a 33-amino-acid-long peptide binds to the dimerization surface, prevents the formation of dimers, and consequently inhibits 17β--HSDcl. Finally, we also show that phage display provides another tool in the search for inhibitors that bind to the surface or in the active site of 17β--HSDcl